Process of controlling the thickness of aluminum deposited on steel wire by controlling the depth of the bath of molten aluminum

ABSTRACT

A BATH OF ALUMINUM IS MAINTAINED AT CERTAIN DEPTHS LESS THAN APPROXIMATELY 2 1/2 INCHES. AT A GIVEN DEPTH BELOW 2 1/2 INCHES A STEEL CORE WIRE IS CONTINUOUSLY MOVED UP VERTICALLY THROUGH THE BATH. THE TEMPERATURE OF THE CORE WIRE AND THAT OF THE BATH AFFECT THE AMOUNT OF ALUMINUM THAT IS RETAINED BY FREEZING ON THE CORE INDEPENDENTLY OF A SUBSTANTIAL RANGE OR WIRE SPEEDS. AT A GIVEN BATH DEPTH LESS THAN 2 1/2 INCHES THE PERCENTAGE OF WEIGHT OF ALUMINUM COATING CLINGING TO THE STEEL CORE MAY BE ADJUSTED SIMPLY BY VARYING THEIR RELATIVE TEMPERATURES.

Feb. 23, 1971 P. A. DION ET AL 3,555,6 71 PROCESS OF CONTROLLING THE THICKNESS OF ALUMINUM DEPOSITED ON STEEL WIRE BY CONTROLLING THE DEPTH OF THE BATH OF MOLTEN ALUMINUM Filed Dec. 15, 1965 2 SheetsSheet 1 Original 15% 300E ZEDM 65% mm? 09 om ow 2 0o IEwo 12m 1 IEwo 15$ :02 m

% LHOIBM 2 Sheets-Sheet 2 P. A. DiON ETAL Feb. 23, 1971 PROCESS OF CONTROLLING THE THICKNESS 0F ALUMINUM DEPOSITED ON STEEL WIRE BY CONTROLLING THE I DEPTH OF THE BATH OF MOLTEN ALUMINUM Original Filed Dec. 15, 1965 United States Patent PROCESS OF CONTROLLING THE THICKNESS OF ALUMINUM DEPOSITED ON STEEL WIRE BY CONTROLLING THE DEPTH OF THE BATH OF MOLTEN ALUMINUM Paul A. Dion, North Attleboro, Mass., and Brian C. Coad,

Oakland, Calif., assignors to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Continuation of application Ser. No. 805,951, Feb. 19, 1969, which is a continuation of application Ser. No. 514,055, Dec. 15, 1965. This application Dec. 17, 1969, Ser. No. 882,399

Int. Cl. C23c N08 US. Cl. 117114 1 Claim ABSTRACT OF THE DISCLOSURE A bath of aluminum is maintained at certain depths less than approximately 2 /2 inches. At a given depth below 2 /2 inches a steel core wire is continuously moved up vertically through the bath. The temperature of the core wire and that of the bath affect the amount of aluminum that is retained by freezing on the core independently of a substantial range of wire speeds. At a given bath depth less than 2 /2 inches the percentage of weight of aluminum coating clinging to the steel core may be adjusted simply by varying their relative temperatures.

This application is a continuation of application Ser. No. 805,951 filed Feb. 19, 1969 which is in turn a continuation of application Ser. No. 514,055 filed Dec. 15, 1965, both now abandoned.

This invention relates to continuous cladding, and more particularly to the continuous cladding of a solid coreforming material by the application thereto and freezing thereon of a melt of a liquid cladding material.

Among the several objects of the invention may be noted the provision of improved control of thicknesses of frozen melt material on solid core material under easily controlled conditions to provide a clad product of superior accuracy; and the provision of convenient apparatus for carrying out the invention. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions and methods hereinafter described, the scope of the invention being indicated in the following claims.

In the accompanying drawings, in which the invention is illustrated,

FIG. 1 is a diagram illustrating certain discoveries upon which the invention is based; and

FIG. 2 is a cross section illustrating apparatus for carrying out the invention.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

It is known to pass continuous lengths of core material such as a metal through a bath of molten metal in order to freeze the molten metal as a cladding onto the surface of the metal core. For example, when comparatively cool steel wire or the like is passed through a hot bath of molten aluminum, the aluminum freezes on the steel surface. Heretofore, coating thickness has been controlled, for example, by adjusting the temperature of the steel entering the bath and the temperature of the molten bath. These two variables and wire speed have heretofore been considered to be the only means by which the coating thickness might be controlled, which is true for the usually excessive bath depths heretofore employed for the molten metal. We have discovered how the cladding thickness can be controlled by changing bath depth so as to make control of wire speed less critical. This is based on the discovery that bath depth under a certain depth is a variable 3,565,677. Patented Feb. 23, 1971 controlling coating thickness independently of core speed in certain comparatively wide speed ranges. By properly controlling bath depth, the coating thickness can be controlled at given bath and wire temperatures substantially independent of the core speed. Thus close tolerances on coating thicknesses can more readily be maintained in certain speed ranges of the core material passing through the melt.

The graph illustrated by FIG. 1 shows the percent weight of aluminum frozen on a steel core wire according to wire speed at a temperature of 1400 F. of the melt or bath. This graph has a main course 1 which shows that at a 2 /2 inch bath depth the weight of aluminum increases with wire speed. From this main course 1 there are two branches 3 and 5 for bath depths of 2 inches and 1 inch, respectively. Thus as to curve 3, over the range of approximately to feet per minute of wire speed, the curve is much flatter than the main course 1. Over the range of approximately 75 to 87 feet per minute, the branch curve 5 is also substantially flatter than the main course 1. Thus it is possible over substantial ranges of core speeds to obtain various constant thicknesses of application of aluminum. It will be understood that the core may enter the bath at any of various selected temperatures, such as room temperature or higher. Such temperature and bath temperature have an effect upon the amount of aluminum picked up by the core.

Referring now to FIG. 2, there is shown means for employing the discovery. Numeral 7 shows a crucible which forms a well 9 into which extends an inlet guiding die 11 for guiding a length of steel wire 13 (for example). The crucible 7 is formed with an internal cylinder 15 for the sliding reception of a hollow piston or plunger 17, provided with connections 19 to a suitable control linkage. The piston 17 is provided with an inverted well 21 terminating in an opening 23 by which the piston has a slidable connection with an outlet passage 25 through which the wire 13 passes upward. By moving the piston 17 up or down, the depth D of the bath through which the wire 13 moves may be controlled. The bath itself is numbered 10.

Thus, according to FIG. 1, for a given wire speed and a given temperature of wire and bath, the percentage of aluminum that will be coated on the wire, using for example a 1-inch depth at D on FIG. 2, will be fairly constant over a substantial range of wire speeds, this being likewise true at a 2-inch depth D, except that a greater weight of aluminum will be picked up and coated. Other depths will result in other weights of aluminum which will be frozen in place; but after a 2 /2 -inch depth is reached, the weight of aluminum accretion becomes dependent not upon bath depth but upon wire speed. The latter is undesirable. The arrangement includes a bulge 12 on die 11 with which the inside lower edge 20 of plunger 19 slidingly engages to limit the maximum depth D to a value such that over a substantial range of core speeds a substantially constant weight of cladding material will be frozen on the core material per lineal inch. Any dimension D less than such a maximum results in other constant but smaller weights frozen on over substantial ranges of core speeds.

As will be appreciated, a cooler wire will tend to have frozen thereon more aluminum. The higher the temperature of the wire, the less aluminum will be frozen on, because as the temperature of the wires approaches that of the aluminum there is a smaller temperature gradient between them.

It will be understood that while the invention has been illustrated by the cladding of aluminum on steel wire, other combinations of materials may be used which would vary the bath depths at which the weight of the cladding on the core would remain substantially constant over a substantial range of core speeds. It will also be understood that other core shapes than the round wire illustrated may be coated.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The method of accurately cladding a length of the steel core wire with aluminum in a selected desired thickness, comprising:

continuously moving the length of wire vertically through a submerged inlet opening in the bottom of a molten bath of aluminum and out of the top surface thereof; maintaining the temperature of the aluminum bath at approximately 1400 F.;

maintaining the moving core wire at a temperature selected to be in the range between room temperature and said bath temperature; and

about 1 to 2 inches and setting the wire speed at a value selected to be within ranges of from approximately 75 to 87 feet per minute at the lesser depth to approximately 85 to 100 feet per minute at the greater depth, whereby a substantially constant desired thickness of aluminum cladding is obtained on the core wire throughout its length.

ALFRED L.

References Cited UNITED STATES PATENTS 5/1884 Sawyer 118-405 5/1923 Schmidt 117115 6/1924 Girvin 117-114 10/1940 Quarnstrom 117114(A)X 12/1944 Wildy et al. 118-405X 10/1950 Lorch et al. 118-405 11/1956 Fish 118-411X 10/1962 Carreker, Jr., et al. 117114X 11/1966 Whitfield 117114(C) LEAVITT, Primary Examiner J. R. BATTEN, In, Assistant Examiner US. Cl. X.R. 

